Process for electroless plating

ABSTRACT

Organo-nitrogen compounds containing at least two nitrogen atoms separated by no more than one carbon atom stabilize electroless plating solutions against plating of the metal on passivated stainless steel and solution decomposition as caused by the presence of impurities such as palladium ion.

United States Patent 11 1 Maguire Feb. 19, 1974 [54] PROCESS FORELEC-TROLESS PLATING 3,310,430 3/1967 Schneble et al. 106/1 Inventor:Eileen g a de ar 3,454,416 7/1969 Heyman et al 106/1 [73] Assignee:Crown City Plating Company, El

Monte, Calif- Primary ExaminerLorenzo B. Hayes [22] Filed: Jan. 2, 1973Attorney, Agent, or Firi'n-Christie, Parker & Hale 211 Appl. No.:320,688

Related US. Application Data [63] Continuation-impart of Ser. No.224,228, Feb. 7-, [57] ABSTRACT 1972, abandoned, which is acontinuation-in-part of Ser. No. 65,685, Aug. 20, 1970, abandoned.

Organo-mtrogen compounds contammg at least two 52 US. 01 106/1, 117/47A, 117/130 E nitrogen atoms sePamed by than One caYbO" 511 1111. C1. c233/02 atom Stabilize electroless Plating Solutions against p 5 Field ofSearch 106/1; 117 [130 E, 47 A, 1 0 R ing of the metal on passivatedstainless steel and solution decomposition as caused by the presence ofim- [56] References Cited purities such as palladium ion.

UNITED STATES PATENTS 2,938,805 5/1960 Ag ens 106/1 10 Claims, N0Drawings i PROCESS FOR ELECTROLESS PLATING BACKGROUND OF THE INVENTIONThis is a continuation-in-part of our-application Ser.

' No. 224,228, filed Feb. 7, 1972, which in turn is a con- Although mostresins are electrically nonconductive, a metal bond to the surface ofthe resin can be established by initial plating operation known aselectroless plating. This is typically accomplished by conditioning thesurface of the resin for plating by contact with a strong oxidizingacid, seeding the conditioned surface by contact with a noble metalsalt, e.g.,

a palladium chloride solution, then immersing the seeded surface in anauto-catalytic electroless plating solution wherein an initial coatingof a conductive metal is established by chemical deposition. The metalcoating formed acts as a buss and allows a thicker metal coating to bebuilt up electrolytically. For most resins, contact with the oxidizingacid is often preceded by a chemical etch to improve the bond strengthof the copper plate.

A typical formulation for an electroless plating solution may beexemplified by an electroless copper plating solution which consistsessentially of a soluble cupric salt, such as copper sulfate; acomplexing agent for the'cupric ion, such as Rochelle salt; an alkalihydroxide for adjusting pl-l; a carbonate radical as a buffer; and areducing agent for the cupric ion such as formaldehyde.

The mechanism by which polymeric objects having surfaces catalyzed bypalladium metal may be plated autocatalytically has been well describedin literature, such as, for example, U. S. Pat. No. 2,874,052.

Electroless plating solutions as described above are, however, subjectto decomposition. For copper plating solutions, for example, the cupricion inherently tends to reduce to the insoluble cuprous form. This maybe overcome, in part, by the use of stabilizers, or by air agitationwhich serves to oxidize cuprous ion back to the cupric state.

Secondary sources of contamination, however, also materially contributeto decomposition. When the cat alyzed plastic article is withdrawn fromthe noble metal salt bath, it too often carries with it, as drag-out,substances including copper, nickel, iron, palladium, gold, silver andeven dust particles, which are catalytic toward solution deoomposition.Palladium ion (Pd is notorious in that if stainless steel tanks orequipment are in contact with electroless (copper) bath even a minuteamount of palladium ion will initiate plating of the copper onto steel.In addition, concentrations as low as one part per million will causespontaneous de- 2 composition of the solution withattendantprecipitation and loss of copper.

It has been proposed to use plastic lined tanks for electroless platingbaths to avoid the problem of plating on the stainless steel tanks. Evenin plastic lined tanks, however, inevitable scratches in the liningresult in initiation of decomposition because the scratches providerecesses within which hydrogen produced during the plating reaction isconcentrated.

Attempts have also been made to stabilize electroless plating baths tominimize decomposition. However, most compounds which have been proposedas stabilizers retardthe rate of electroless plating. While heating maybe employed to increase the rate of deposition, it has not'beengenerally used because heating also promotes decomposition.

We have employed an alternate route to minimize loss of valuablechemicals through decomposition of the plating solutions. This involvesthe use of two plating baths. One is a strike bath in which a noblecatalyzed surface is initially plated in a bath essentially free ofinhibitors. The other is a plating bath in which the surface platedarticle is further electrolessly plated and which is inhibited to theextent that if the article having the catalytic noble metal surface werepassed directly into the bath without first passing through the strikebath, no plating metal would be deposited on the article. In thissystem, the plating bath remains stable while the strike bathcontinuously decomposes. The volume of the strike bath, however, is lowwith respect to the volume in the plating bath and losses have beenminimized.

SUMMARY OF THE INVENTION It has now been found that organo-nitrogen compounds containing the radicals or groups:

serve as effective stabilizers to prevent contaminant decomposition ofelectroless plating solutions. Their presence in the solution remarkablyincreases solution tolerance for palladium and other impurities whichnormally causes solution decomposition or plating of the metal on thestainless steel surfaces. The compounds embraced are those which aresoluble in water or a dilute base in quantities sufficient to complexwith palladium ion.

When used alone or in conjunction with other stabilizers or a source ofoxygen to oxidize cuprous ions in an electroless copper plating solutionback to the cupric state, the organonitrogen compounds of this inventionwill stabilize electroless copper plating solutions for long periods oftime. In use, amounts which will permit deposition of a plate onto thesurface of a suitably catalyzed article within 30 seconds afterimmersion, will stabilize electroless copper plating solutions in thepresence of palladium ions at concentrations well in excess of thatwhich could be reasonably expected to be dragged-in in 48 hours provideda source of oxygen is present. When some of the stabilizer is consumedin coping with contaminants, additional quantities can be added withoutretarding deposition rate.

While useful for any electroless plating solution the stabilizers ofthis invention are preferably used as stabilizers for the strike bath ofa two-bath system wherein a thin film of plating metal is deposited in astrike bath,

followed by additional plating in a plating bath inhibited to the extentthat if non-conductive articles having a catalytic noble metal film wereimmersed in the solution no plating would occur.

DESCRIPTION According to the present invention, there is providedorgano-nitrogen stabilizers for electroless plating solutions whichmaterially increase the tolerance of the electroless plating solutionsfor metallic ions and other impurities which normally cause solutiondecomposition.

The organo-nitrogen compounds which are used to stabilize electrolessplating solutions according to the practice of this invention arecompounds which contain at least two nitrogen atoms separated by no morethan one carbon atom and in particular radicals or groups:

\N-C-N/ :and N=CN H H I The argnanieagfi coin bunas'ebn'taiaih the aboveradicals which are useful in accordance with this invention are thosewhich are soluble in water or a dilute base in quantities sufficient tocomplex with palladium ion and still permit deposition of a plate ofcopper onto a noble metal catalyzed surface,

Illustrative of the organo-nitrogen compounds containing the radicalbenzo tria z ol e? amidolfnitrosarnino amidino)- l tetrazene;S-methylbenzotriazole; guanazolo; 1,2,3- triazole; tetrazole;4,5-triazole carboxylic acid; aminotetrazole and the like.

The above organo nitrogen compounds may be classified generally as 1,2,3triazoles and tetrazoles and in most instances are part of a ringstructure.

Of the organo nitrogen containing the group:

which may be classified as amidines there may be mentioned:

creatininu CH3 H A i H e--1 c=NrI 1 1 (III) creatlne NH:

I I-CH:-CQOH Ha (1v) guanldine NH: NH

I IH (V) aminoguanidine? dipheriylguanidine; 1 ,1 ,3 ,3 tetramethylguanidine; guanine, guanilic acid, phenylbiguanidine, guanosine,streptidine and the like. Of these guanidine and aminoguanidine arenormally-provided in a salt form, in particular, as the carbonate salt,but the salt group has no influence on their functionality.

Of the organo nitrogen compounds containing the group which maytypicallybe lQi i friaizoles', diaz oles and pyrimidines there may bementioned imidazole;

HC--N CH V N-C v1) Xanthine; 3-amino -(ll-l)-l, 2,4-triazole; 2-aminopyrimidine; melamine; benzoguanamine; phenazopyridine; folic acid;2-amino-4(3H)- pyrimidone; 1,2,4 triazole; 2-aminopyridine; 2-amino-4-methylpyrimidine; and the like.

Of these, compounds containing the groups:

have been found to be the most effective and are preferred. I

Benzotriazole which has been found to stabilize electroless platingsolutions at Pd concentrations of ppm or more when present in an amountof only about 0.005 grams per liter of solution is most preferred.

While no wise bound by theory, it is believed that the free electronsavailable from the closely associated trivalent nitrogen atoms in theorgano-nitrogen stabilizers of this invention in some way complex,possibly as a chelate, with divalent palladium ions as well as otherforeign metallic ions which may be introduced in the electroless platingsolutions in the drag-out. They, also have been found to complex orchelate cuprous ions.

The organo-nitrogen stabilizers of this invention do not, however,appear to stabilize against the normal solution decomposition as, forexample, the natural reduction of cupric ion to the cuprous state, butas indicated, do chelate them. Accordingly, for long solution stabilityand conservation of the organo nitrogen compounds to cope with palladiumions they should be used with another system which prevents normalreduction of the plating metal ions. For electroless copper solutions,the presence of another stabilizer and/or source of oxygen to oxidizecuprous ions back to the cupric state is suggested. The stabilizers ofthis invention may, for instance, be conveniently used in conjunctionwith air-agitated solutions wherein air is drawn into the solution bymere agitation or bubbled through the solution to stabilize cupric ionagainst reduction to the cuprous state. Equally convenient is tointroduce oxygen through oxidizing compounds such as sodium peroxide,hydrogen peroxide, chromic acid, sodium bromate, potassium bromate,sodium perborate, potassium perborate, sodium chlorate, potassiumchlorate and the like.. 'wfi'iietfie'aigaad aitm efieoimsomias ofmains/ention do stabilize electroless plating solutions againstdecomposition due to the presence of foreign substance, they do nothinder deposition onto a suitably catalyzed plastic substrate. At theconcentrations shown in Table l, for instance, a uniform deposition of acopper plate onto a catalyzed plastic substrate will begin within 30seconds after immersion. Yet, the solutions will remain stable at thepalladium ions concentration shown for at least 24 hours at roomtemperature in that decomposition or plating on steel will not occurprovided there is present a source of oxygen to prevent normal reductionof cupric ions to the cuprous state.

ln the absence of a source of oxygen, stabilization time will be reducedsince some of the organo-nitrogen compounds present will be consumed incoupling cuprous ions formed by the natural reduction of cupric ions.

TABLE I Stabilizer Conc. g/liter Pd"*(ppm) Benzotriazole 0.005 lCreatinine 0.009 85 Creatine 0.3 80 Guanidine Carbonate 0.02 l00lmidazole 0.1 45

While the organo-nitrogen stabilizers of this inve n j tion arepreferably used in the strike bath of a two-bath group also darkens asstabilizer concentration increases and may, at certain concentration,terminate copper deposition after an initial plate, possibly due to thefor mation of film. This film, however, can be easily re.

moved in an acid wash for additional electroless plating in another bathor in an electrolytic plating bath.

As will be appreciated by one skilled in the art, the amount ofinhibitor to be incorporated in a bath may be broadly varied.Electroless plating baths are generally continuously replenished as themetals are consumed as a consequence of plating. Accordingly, thesolution need only be stabilized against the estimated amount of foreignmaterials which will be brought into the solution between periods ofaddition of replenishing solutions and fresh stabilizers.

As indicated, although the inhibitors of this invention may be used inconventional single bath copper and nickel plating systems, when themetal is at least copper we prefer to use them in the strike bath of atwo-bath plating system hereinafter described.

Generally, the two-bath plating process involves forming an initialcopper plate on the catalyzed surface of a suitably conditioned plasticarticle in strike bath inhibited with the organo-nitrogen stabilizers ofthis invention followed by a buildup of electroless plated copper in ahighly inhibited plating bath.

As indicated, the organo-nitrogen stabilizers of this invention are atleast used in the strike bath. The strike bath serves to provide aninitial plate. The article is then passed into a highly stabilizedplating bath. The concentration of inhibitor in theplating bath beingsuch that, if the article having a catalytic noble metallic surface werepassed directly into the plating bath without first passing through thestrike bath, no plating metal would be deposited on the article.

Using the organo-nitrogen inhibitors of this invention, the compositionof the strike bath may be any of those conventionally employed forelectroless deposition of copper on a non-conductive article.Formulations of room temperature electroless copper plating bathsinclude, for example, the following general composition for an aqueoussolution:

MOLARCONCENTRATION lNGREDlENT Soluble Cupric Salt 0.02-0.l5 ComplexingAgent 0.03-0.75 Reducing Agent 0.05-l.50 pH Adjustm- Sufficient to givepH from about ll.5 to 14 I The concentrations of complexing agent andreduc- 0 ing agent are somewhat related to the concentrations of cupricion in solution.

As the water soluble cupric salt there may be employed copper sulfate,cupric halides, cupric nitrates, cupric acetates, and other inorganicand organic cupric salts. Copper sulfate and cupric chloride arepreferred.

As comp lexing agents for the cupric ion there may be employed Rochellesalts, the mono-, di-, tri-, and tetrasodium salts ofethylenediaminetetracetic acid; the ethanolamines, such astriethanolamine; nitrilotriacetic acid and its alkali metal salts;gluconic acid; gluconates; glucono-y-lactone; N-hydroxyethyleneethylenediaminetriacetate; hydroxyalkyl substituted dialkylenetriamines, such as pentahydroxypropyl diethylenetriarnine; thesalicilates; citrates; lactones, and other complexing agents well knownin the art.

As reducing agents there may be employed formaldehyde and its precursorsor derivatives such as paraformaldehyde; glyoxyl; borohydrides, such asalkali 7 be operated at an elevated temperature without signifi cantdecomposition. Accordingly, the high plating rates are obtained by theuse of both baths without attendant .loss of valuable chemicals andproduction problems. More specifically, a detailed description of thetwobath process solution utilizing the organo-nitrogen stabilizers ofthis invention may be made in terms of the history of the electrolesscopper plating of a molded plastic article such as an ABS article.

The molded plastic article is normally cleaned, preetched with anorganic chemical solvent, if required, and then etched in an etchingchemical bath such as a mixture of chromic and sulfuric acids. Aftercleaning of the etched article, including rinsing in an alkalinecleaner, the article is sensitized in a stannous chloridehydrochloricacid bath and then activated in a bath of a noble salt, such aspalladium chloride, to provide a catalytic noble metal on the surface ofthe plastic. Following rinsing to remove excess palladium from thesurface of the article, it is passed into the stabilized strike bath.

The organo-nitrogen stabilized strike bath can be an electroless copperplating solution having a formulation such as the following:

INGREDIENT CONCENTRATION Rochelle Salt 34 grams/liter Caustic Soda l2grams/liter Copper Sulphate 7 grams/liter Sodium Carbonate 6 grams/literFormaldehyde (Formalin) 25 cc./liter Organo-nitrogen Stabilizer ppm PdWater Sufficent to make I liter The strike bath is typically maintainedat room temperature. The plastic article with palladium metal on itssurface is immersed in the strike bath ,for from about 30 seconds toabout 3 minutes and then removed. This is a sufficient period ofimmersion to enable deposition of a thin copper film over the entiresurface of the article. The strike bath, in addition to preparing thearticle for deposition in the electroless plating bath, also serves as acollector for the bulk of the metallic contaminants which otherwisewould pass directly into the plating bath, these contaminants beingcomplexed by the organo-nitrogen stabilizers.

Upon removal from the strike bath, the plastic article having a thincopper deposit is passed directly into the electroless plating bath. Inorder to increase the rate of plating as described above, this bath ismaintained at an elevated temperature, preferably a temperaturesomewhere in the range from 90 to 140F.- An example of a formulation forthe preferred plating bath is as follows:

Sufficient to stabilize against 20-80 Continued I INGREDIENT. MOLARCONCENTRATION Free Sodium Hydroxide 0.l25 Potassium Cyanide 0.006

Water Sufficient to make 1 liter The free sodium hydroxide referred toabove is that quantity which is in addition to the amount required toform the chelate and to convert the sodium bicarbonate in the solutionto'sodium carbonate.

The plastic article is retained in the electroless plating bath for aperiod of from 3 to 6 minutes. During this period of time, additionalthicknesses of copper sufficient to permit subsequent electrolyticmetallic plating are deposited. After removal from the electrolessplating bath, the article is rinsed and soaked, and, if electrolyticplating is required, is passed to the electroplating process.

Through the use of the organo-nitrogen stabilizers of this invention, ahighly stabilized, nonsensitive formulation can be used in both thestrike and plating baths without significant decomposition over itsservice life. Further, as indicated, solutions can be used in stainlesssteel tanks with stainless steel heaters and filters. As a result of thestability imparted to both baths, roughness or so-called bumps in theplating deposit are avoided and the plating bath can be operated atelevated temperatures with attendant improvements in production rateeconomies.

EXAMPLE 1 To a series of electroless copper solutions having theformulation:

CuSO.-2H O 7.5 gr.

Rochelle Salt 29.0 gr.

NaOH (free) 12.0 gr.

NaHCO; 9.4 gr.

Formaldehyde 10.75 gr.

Sufiicient to make 1 liter Water A solution under the same conditionswithout the stabilizers began to plate on the stainless steel uponintroduction of Pd and spontaneously decomposed at l 'd concentrationsof less than 1 ppm.

Under identical conditions, plating on the steel began at 8 ppm Pd whenpyridine was present in a concentration of 0.5 gr/l. and at a l 'dconcentration of 1 ppm when morpholine was present at a concentration of1.0 gr/l.

Decomposition occurred at a Pd concentration of 1 ppm when dimethylformamide a H-iJ-N and dimethylacetamide O CH! CHa-Pl-N were present inquantities of 1 cell.

EXAMPLE 2 Tests were performed to compare the stabilizing activity ofthe organo-nitrogen compounds of the invention alone and in conjunctionwith other known stabilizers.

The base plating solution employed in each test had the followingcomposition:

Copper Sulfate (CuSOrSIhO) 7.5 gr/l Sodium Bicarbonate 9.4 gr/l RochelleSalt 28.0 gr/l Formaldehyde (Formalin) 26.0 cc/l Free Sodium Hydroxide12.0 gr/l Balance Water plus stabilizers In each instance ppm palladiumchloride was added to the solution with stirring. No further agitationwas employed.

In each instance a suitably catalyzed ABS resin plaque was electrolesslyplated by immersion in the solution for 5 minutes at a temperature of70F 75F TABLE III Stabilizer System Decomposition Time PotassiumAntimony Tartrate 40 min. 2'2-biquinoline 27 min. Benzotriazole 4 hr.Benzotriazole+Potassium Antimony 4 hr. TartrateBenzotriazole+2'2'-biquinoline 4 hr. Creatinine 165 min.Creatinine+Potassium Antimony Tartrate 200 min.Creatinine-l-Z'Z'-biquinoline 2 hr.

CONTROL. I

To establish the uniqueness of the organo nitrogen compounds of thisinvention to cooperate with a source of oxygen to induce maximum bathstability, 2'2- biquinoline and potassium antimony tartrate were testedunder'conditions as set forth in Example 1.

In these tests there was initially added 2 ppm Pd as palladium chlorideand if no solution breakdown occurred an additional part per million Pdwas added about every 15 minutes.

For 2'2-biquinoline at a solution concentration of 0.01 gr/l thesolution in the presence of air agitation and type 304 stainless steeldecomposed upon the addition of 2 ppm palladium ion.

For potassium antimony tartrate at a solution concentration of 0.03gr/liter, upon the addition of 15 ppm Pd solution breakdown occurred.The period of time involved was slightly in excess of 3 hours.

CONTROL II To further evaluate potassium antimony tartrate it wasdetermined the maximum amount which would permit a complete deposit ofcopper on a plaque of a catalyzed ABS resin within 30 seconds at roomtemperature from a solution prepared according to Example 1 in which itwas used as the stabilizer. This concentra- 'tion was determined to beagain 0.03 gr/l.

Employing the conditions of Example 1, various quantities of Pd wereadded to samples. While maintaining air agitation the solutions wereallowed to stand for 7 hours. The results are shown in Table IV.

The sample was judged not stable when plating of copper on stainlesssteel occurred.

These tests establish that the electroless copper plating solutioncontaining potassium antimony tartrate has tolerance for less than ppmPd in the presence of stainless steel even when aided by air agitation.

EXAMPLE 3 TABLE V Organo Nitrogen Compound Conc. gr./l.

Benzotriazine 0.006 Amminoguanidine (bicarbonate) 0.02 3amino-(1H)-l,2,4 triazole 0.02 diphenylguanidine 0.02 Melamine 0.007Benzoguanamine 0.02

In each instance the prepared solution permitted copper decompositiononto an immersed catalyzed substrate in about 30 seconds. However thetotal immersion time in each instance was about 1.5 minutes. In eachinstance a uniform plate of copper was deposited.

What is claimed is:

1. In a process for electroless copper plating which comprises immersinga surface which is receptive to electroless deposition of copper in analkaline aqueous bath containing a water soluble cupric salt; acomplexing agent for cupric ions; an alkali metal hydroxide formaintaining solution pH between about 11.5 and I4, and a reducing agentfor cupric ions the improvement which comprises the use of stabilizingamount of at least one organo-nitrogen compound containing a groupselected from the groups consisting of H NH \NI!IN/; --N=N--N N- N andN=( 3-N .v X

the organo-nitrogen compound being present in an amount sufficient tostabilize the bath against decomposition due to the presence of at leastpalladium ion but insufficient to terminate copper deposition.

2. A process as claimed in claim 1 in which another stabilizer ispresent.

3. A process as claimed in claim 1 in which an oxidizing agent forcuprous ion is present.

4. A process as claimed in claim 2 in which the oxidizing agent isoxygen.

5. In a process for electroless copper plating which comprises immersinga surface which is receptive of electroless deposition of copper in analkaline aqueous bath containing a water soluble cupric salt, acomplexing agent for cupric ions, an alkaline metal hydroxide formaintaining solution pH between about 11.5 and 14, and a reducing agentfor cupric ions, the improvement which comprises the use of astabilizing amount of at least one organo-nitrogen compound selectedfrom the group consisting of benzotriazole, creatinine, creatine,guanidine, imidazole, benzotriazine, aminoguanidine, 3 amino-( lH)-l,2,4triazole, diphenyl guanidine, melamine and benzoguanamine, theorganonitrogen compound being present in an amount sufficient tostabilize the bath against decomposition due to the presence of at leastpalladium ion but insufficient to terminate copper deposition.

6. A process as claimed in claim 5 in which an oxidizing agent forcuprous ion is present.

7. A process as claimed in claim 6 in which the oxidizing agent isoxygen.

8. In an aqueous alkaline electroless copper plating solution comprisinga soluble cupric salt, a complexing agent for cupric ion; an alkalimetal hydroxide to maintain solution pH between about 1 1.5 and 14, areducing agent for cupric ion and a source of oxygen to oxidize cuprousions back to the cupric state, improvement comprising at least oneorgano-nitrogen compound containing a group selected from the groupsconsisting of said organo nitrogen compound being present in solution inan amount sufficient to stabilize the solution against decomposition dueto the presence of at least palladium ion but insufficient to preventcopper deposition onto a surface receptive to copper deposition.

9. In an alkaline electroless copper plating solution comprising asoluble cupric salt; a complexing agent for cupric ions; an alkali metalhydroxide for pH control and a reducing agent for cupric ions, theimprovement comprising an amount of benzotriazole sufficient tostabilize the solution against decomposition due to the presence of atleast palladium ion but insufficient to terminate copper deposition ontoa surface receptive to copper deposition.

10. In an aqueous alkaline electroless copper plating solutionconsisting of water, a soluble cupric salt, a complexing agent forcupric ion, an alkali metal hydroxide to maintain solution pH betweenabout 11.5 and 14, a reducing agent for cupric ion and a source ofoxygen to oxidize cupric ions back to the cupric state, the improvementcomprising at least one stabilizer selected from the group consisting ofbenzotriazole, creatinine, creatine, guanidine, imidazole,benzotriazine, aminoguanidine, 3 amino-(ll-I)-l,2,4 triazole,diphenylguanidine, melamine and benzoguanamine present in solution in anamount sufficient to stabilize the solution against decomposition due tothe presence of at least palladium ion but insufficient to preventdeposition of copper onto a surface receptive to copper deposition.

l II l UNITED STATES PATENT OFFICE- CERTIFICATE OF CORRECTION Patent N0.3.793. .03 8 Dated Febr gy 19, 1974 Inventor) Leon A. .Kadison andEileen Maguire It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Inventor reads as "Eileen Maguire", should read as Leon A. Kadison andEileen Maguire Column 1, line 62, "decomposition" should bedecomposition Column 7, line 38,'- "25 cc./liter" should be 25 'ccs/liter t fiolumn 11, line 14, I "Zhours" should be 24 hours Signed andsealed this 10th day f September" 197 (SEAL) Attest:

McCOY M. GIBSON, JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. A process as claimed in claim 1 in which another stabilizer ispresent.
 3. A process as claimed in claim 1 in which an oxidizing agentfor cuprous ion is present.
 4. A process as claimed in claim 2 in whichthe oxidizing agent is oxygen.
 5. In a process for electroless copperplating which comprises immersing a surface which is receptive ofelectroless deposition of copper in an alkaline aqueous bath containinga water soluble cupric salt, a complexing agent for cupric ions, analkaline metal hydroxide for maintaining solution pH between about 11.5and 14, and a reducing agent for cupric ions, the improvement whichcomprises the use of a stabilizing amount of at least oneorgano-nitrogen compound selected from the group consisting ofbenzotriazole, creatinine, creatine, guanidine, imidazole,benzotriazine, aminoguanidine, 3 amino-(1H)-1,2,4 triazole, diphenylguanidine, melamine and benzoguanamine, the organo-nitrogen compoundbeing present in an amount sufficient to stabilize the bath againstdecomposition due to the presence of at least palladium ion butinsufficient to terminate copper deposition.
 6. A process as claimed inclaim 5 in which an oxidizing agent for cuprous ion is present.
 7. Aprocess as claimed in claim 6 in which the oxidizing agent is oxygen. 8.In an aqueous alkaline electroless copper plating solution comprising asoluble cupric salt, a complexing agent for cupric ion; an alkali metalhydroxide to maintain solution pH between about 11.5 and 14, a reducingagent for cupric ion and a source of oxygen to oxidize cuprous ions backto the cupric state, improvement comprising at least one organo-nitrogencompound conTaining a group selected from the groups consisting of
 9. Inan alkaline electroless copper plating solution comprising a solublecupric salt; a complexing agent for cupric ions; an alkali metalhydroxide for pH control and a reducing agent for cupric ions, theimprovement comprising an amount of benzotriazole sufficient tostabilize the solution against decomposition due to the presence of atleast palladium ion but insufficient to terminate copper deposition ontoa surface receptive to copper deposition.
 10. In an aqueous alkalineelectroless copper plating solution consisting of water, a solublecupric salt, a complexing agent for cupric ion, an alkali metalhydroxide to maintain solution pH between about 11.5 and 14, a reducingagent for cupric ion and a source of oxygen to oxidize cupric ions backto the cupric state, the improvement comprising at least one stabilizerselected from the group consisting of benzotriazole, creatinine,creatine, guanidine, imidazole, benzotriazine, aminoguanidine, 3amino-(1H)-1,2,4 triazole, diphenylguanidine, melamine andbenzoguanamine present in solution in an amount sufficient to stabilizethe solution against decomposition due to the presence of at leastpalladium ion but insufficient to prevent deposition of copper onto asurface receptive to copper deposition.